1. Field of the Invention
The present invention relates to a zoom lens and an image pickup apparatus including the same, which are suitably used for an image pickup apparatus such as a video camera, a digital still camera, a monitoring camera, a film camera, and a broadcasting camera.
2. Description of the Related Art
It is required for a zoom lens to be used in an image pickup apparatus to have a high zoom ratio and a small size. A positive lead type zoom lens including five or more lens units in which a lens unit having a positive refractive power is arranged closest to an object side is known as a small-sized zoom lens having a high zoom ratio. In addition, a rear focus type zoom lens is known as a zoom lens with which an entire optical system is relatively easily downsized. In the rear focus type zoom lens, lens units other than a first lens unit are configured to move in an optical axis direction, to thereby carry out focusing.
In addition, in recent years, a zoom lens has been demanded to achieve high-speed autofocus, a so-called full-time manual operation in which autofocus and manual focus are used together in real time, and the like.
As a zoom lens for realizing such demands, there is known a zoom lens including, in order from an object side to an image side, first to fifth lens units respectively having positive, negative, positive, positive, and negative refractive powers. In Japanese Patent Application Laid-Open No. H10-206736 and Japanese Patent Application Laid-Open No. 2009-168934, there is disclosed a zoom lens in which zooming is carried out by moving lens units and focusing is carried out by moving a fifth lens unit. In addition, a six-unit zoom lens is known, which includes, in order from an object side to an image side, first to sixth lens units respectively having positive, negative, positive, negative, positive, and negative refractive powers.
In Japanese Patent Application Laid-Open No. H11-174324, there is disclosed a zoom lens which carries out focusing from infinity to a short distance by moving a first lens unit to an object side. In addition, there is also disclosed a zoom lens which carries out focusing by moving a fourth lens unit and a sixth lens unit. In Japanese Patent Application Laid-Open No. 2011-180218, there is disclosed a zoom lens which carries out focusing by moving a sixth lens unit. In addition, there is known a seven-unit zoom lens including, in order from an object side to an image side, first to seventh lens units respectively having positive, negative, positive, negative, positive, negative, and positive refractive powers. In Japanese Patent Application Laid-Open No. 2004-317867, there is disclosed a zoom lens which carries out focusing by moving a sixth lens unit.
In order for a telephoto zoom lens including five or more lens units to easily obtain high-speed focusing and achieve a less aberration variation during focusing and high optical characteristic over an object distance, it becomes important to appropriately set the refractive powers of the lens units.
In addition, it becomes important to appropriately set the refractive powers, the lens structure, and the like of the lens units for focusing. When those structures are not appropriately set, it becomes difficult to carry out focusing at high speed and obtain high optical characteristic over the object distance from the infinity to the short distance.